Question

What are the three main types of radioactive decay?

Answer 1

Well, there are four... here are simplified descriptions of them.

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ALPHA DECAY

Emission of a helium-4 nucleus.

Example:

`""_(92)^(238) "U" -> ""_(90)^(234) "Th" + ""_(2)^(4) "He"`

This is favored for atomic number higher than `83`. Here the mass number drops by `4` and atomic number drops by `2`.

BETA DECAY

A neutron splits into a proton and electron and emits the electron.

`""_(0)^(1) n -> ""_(1)^(1) p + ""_(-1)^(0) e`

This is favored for an `N/Z` ratio too high. This is the only one where the atomic number increases by `1`.

POSITRON EMISSION

A nuclide emits a positron, i.e. an electron-sized proton.

Example:

`""_(6)^(11) "C" -> ""_(5)^(11) "B" + ""_(1)^(0) e`

This is favored for an `N/Z` ratio too low. This drops the atomic number by `1` for light nuclei.

ELECTRON CAPTURE

A core electron absorbs into the nucleus and combines with a proton, forming a neutron.

`""_(1)^(1) p + ""_(-1)^(0) e -> ""_(0)^(1) n + "X-ray"`

This is favored for an `N/Z` ratio too low. This drops the atomic number by `1` but is favored by heavy nuclei.